- Will the DAP-1522 bridge with the DIR-645 (yes, shouldn't be an issue)
- Will the DAP-1522 work as an AP in conjunction with the DIR-645 (yes, assuming the DAP is hardwired to the 645)
- Will the DAP-1522 work as a repeater (no, doesn't have this function)
In terms of extending the range of your network the DAP-1522 can be used as a bridge however the range may be limited to an extent. With wireless communication both devices need adequate strength and gain to both send and receive.
In a medium sized home the DAP-1522 with the DIR-645 it should be fine however, there is almost a definite chance that the throughput and signal strength would be better with the DIR-645 with a DAP-1525 in bridge mode since both use smartbeam.